1. Field of the Invention
The present invention relates to reduction of power consumption in a semiconductor device capable of selecting an external supply voltage.
2. Description of the Prior Art
One of the characteristics in most semiconductor devices having been recently designed is that various functions are provided to the semiconductor device for harmonization with an external system. The aforementioned semiconductor device is generally called a multifunctional semiconductor device. The reason for manufacturing the multifunctional semiconductor device as described above is because it is necessary to consider the situations of a market requiring a semiconductor device or a relation with a peripheral circuit of a system using a semiconductor device. For example, in a memory device, an option is provided so that a data width can be selected among X32, X16 and X8 or an external supply power can be selected between 1.8V and 2.5V.
However, in contrast with other options, when one of different external supply powers is selected and used in a semiconductor device, consumption power may become problematic.
This will be described in detail with reference to FIG. 1.
FIG. 1 is a block diagram schematically showing the general construction of a semiconductor device selecting and using one of different external supply powers.
As shown in FIG. 1, the semiconductor device basically includes a 1.8V dedicated block 11 and a 2.5V dedicated block 12. The 1.8V dedicated block 11 receives an external input signal and converts the received signal to an internal signal used in the semiconductor device when an external voltage is selected to be 1.8V. The 2.5V dedicated block 12 receives an external input signal and converts the received signal to an internal signal used in the semiconductor device when an external voltage is selected to be 2.5V. Herein, FIG. 1 shows only an example. Also, the voltage level of the external voltage may change according to the types of semiconductor devices and three or more types of external voltages may be applied to the semiconductor device. A signal selector 13 selects signals outputted from the 1.8V dedicated block 11 and the 2.5V dedicated block 12 and transfers the selected signals to the internal circuit. Further, the signal selector 13 is typically constructed by a circuit having a switching function like a multiplexer.
Hereinafter, the operation of the internal circuit shown in FIG. 1 will be described.
First, when an external supply voltage applied for operating the semiconductor device including the internal circuit shown in FIG. 1 is selected to be 1.8V, the 1.8V dedicated block 11 is selected. Accordingly, input signals applied to the semiconductor device are transferred to the signal selector 13 via the 1.8V dedicated block 11.
In contrast, when the external supply voltage is selected to be 2.5V, the 2.5V dedicated block 12 is selected. Accordingly, the input signals applied to the semiconductor device are transferred to the signal selector 13 via the 2.5V dedicated block 12.
However, in the prior art, as shown in FIG. 1, the 1.8V dedicated block 11 is operated by the supply power Vperi and the ground voltage Vss and the 2.5V dedicated block 12 is operated by the external supply power VDD the ground voltage Vss. Herein, the supply power Vperi is an internal voltage generated when the semiconductor device is powered-up and the external supply power VDD is a voltage applied from an external of the semiconductor device.
By this reason, even after the 1.8V dedicated block 11 has been selected, the external supply power VDD the ground voltage Vss are supplied to the 2.5V dedicated block 12, thereby causing unnecessary power consumption.
Similarly, even after the 2.5V dedicated block 12 has been selected, the supply power Vperi the ground voltage Vss are supplied to the 1.8V dedicated block 11, thereby causing unnecessary power consumption.